Many modern integrated circuit devices include on-die capacitors (ODC). In typical configurations, the ODC is coupled between two power railings, with one power rail being at a higher voltage level than the other power rail. However, high voltage differences between the two power railings can cause reliability concerns, namely due to the breakdown of dielectric material within the ODC.
In some scenarios, the ODC is formed using two or more serially connected capacitors such that each capacitor receives only a portion of the supplied voltage. While such an ODC can overcome the reliability issue, ODCs formed using two or more capacitors can exhibit other non-idealities such as a floating metal plate issue that arises when a metal plate of one of the capacitors is not coupled to any particular voltage or power rail, which causes the metal plate to be at a floating voltage level. The floating metal plate issue is undesirable in most modern integrated circuit devices as floating plates can trap charges and alter the capacitance value of the capacitor.
One typical solution for overcoming the floating metal plate issue is to couple the metal plate to an antenna diode. However, such a solution can increase the number of connections to the on-die capacitors, which may not be preferable and can consume excessive space within the integrated circuit. Another known solution to the floating metal plate issue is to “weakly” couple the floating metal plate to a power rail in which an indirect connection is formed between the floating metal plate and the power rail. However, such a solution can require complex and area-consuming interconnections in order to weakly couple the floating metal plate to the power rail.
It may therefore be desirable to be able to provide improved on-die capacitor structures.